Long-Term Rate-Based User-Centric Association for Downlink Multi-Antenna HetNets

The dense deployment of current cellular networks, and the envisioned densification of fifth-generation new-radio (5G-NR) have made the cost of centralized and optimized user association algorithms prohibitive. In contrast, using a standard max-power association can degrade the user's rate due to network load imbalance. To this end, we develop a user-centric association algorithm for downlink multi-antenna heterogeneous cellular networks (HetNets). The algorithm maximizes a function of the expected long-term rate, which depends on the multi-antenna transmission mode used during data communications. The proposed algorithm uses an overhead of the same order as max-power association, requiring minimal changes to the cell selection procedure used in existing cellular networks. Indeed, the user merely measures the received signal power from base stations (BSs) in vicinity, processes these measurements to approximate the expected rate from each BS, and then connects to the one with the highest estimated value. We evaluate the algorithm in a dense tiered network with a realistic 3GPP channel model. Simulation results show that the average user rate improves under the proposed algorithm since it utilizes the multi-antenna transmission mode unlike the conventional max-power association.